Circuit for distributing power between two mutually orthogonal polarization paths employing a rotatable absorbing strip



Oct. 27, 1964 F. c. DE RONDE 3,154,754

CIRCUIT FOR DISTRIBUTING POWER BETWEEN TWO MUTUALLY ORTHOGONALPOLARIZATION-PATHS EMPLOYING A ROTATABLE ABSORBING STRIP Filed Nov. l0.1960 INVENTOR FRANZ CH. DE RONDE United States Patent O 3,154,754CIRCUIT FOR DISTRIBUTING PWER BETWEEN TWG MUTUALLY RTHOGONAL POLARIZA-'HON PA'IHS EMPLOYING A ROTATABLE AB- SORBWG STRIP Frans Christiaan deRonde, Eindhoven, Netherlands, as-

signor to North American Philips Company, Inc., New York, NY., acorporation of Delaware Filed Nov. 10, 1961i, Ser. No. 68,496 Claimspriority, application Belgium Dec. 16, 1959 3 Claims. (Cl. 333-7) Theinvention relates to a power dividing circuit `for microwaves.

A power dividing circuit is known which comprises lirst transmissionpath for electromagnetic waves having a certain direction lofpolarisation. This power divider further comprises a second transmissionpath 1for electromagnetic waves and a third transmission path forelectromagnetic waves, the electromagnetic waves in the second landthird transmission paths lbeing polarised at right angles to oneanother. The rst transmission path is connected to the second and thirdtransmission paths through a cornmon polarisation rotator. It is furtherknown to use a twisted strip of conductive material as a polarisationrotator. The known power divider provided with the said knownpolarisation rotator has a limitation in that the second and thirdtransmission paths are coupled with yone another.

It is the object of the invention to eliminate this coupling.

According to the invention, at the end of the strip adjacent the secondand third transmission paths and in alignment therewith a strip isprovided made o-f a material for absorbing electromagnetic waves havinga direction of polarisation parallel to the plane of this strip.

The invention will now be explained more fully with reference to thedrawing.

FIG. 1 shows by way of example an embodiment of a power divider inaccordance with the invention.

FIGS. 2 and 3 show vector diagrams illustrating the operation off thepower distributor of FIG. l.

In FIG. 1 a wave guide 1 of rectangular cross-section is connected to awave guide 2 of circular cross-section through a matched transitionpiece 3. The wave guide 2 contains a strip S1 of conductive material.This strip iS secured to the inner surface of the wave guide 2 by meansof projections 4 and 5. The points of attachment lie in a plane passingthrough the axis of wave guide 2, in the case shown in the plane `of thedrawing. At its other end the strip S1 is :secured to the inner surfaceof 'a cylinder C with the aid of projections 7 and 8. The inner `surfaceof the cylinder C is linked yup with the inner surface of the wave guide2 without reflection. The cylinder C is adap-ted to be rotated about itsaxis which coincides with the axis of the wave guide 2. By turning thecylinder C relatively to the cylinder 2 the strip S1is twisted; as willbe explained hereinafter, the maximum relative angular displacement ofthe cylinder C need not exceed 90.

The strip S1 and the cylinder C together constitute a variablepolarisation rotator for electromagnetic waves.

A strip S2 is aligned with the strip S1. This strip S2 is made of amaterial, for example a metal deposed from vapour, ,for absorbingelectromagnetic energy. In the position of the cylinder C shown in FIG.1 both the strip S1 and the strip S2 lie in the plane of the drawing.

The wave guide `2 further contains a coupling member 9 forelectromagnetic waves the direction of polarisation of which lies in theplane of the drawing at right angles to the axis of the Wave guide 2.This coupling member comprises a conductive rod 10 which through anaperture 11 in the wave guide 2 extends into a Wave guide 12 shownpartly only.

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The rod 10 lies in a plane passing through the axis of the wave guide 2at right angles to the axis. A strip S3 of conductive material isarranged behind the rod 10 spaced away therefrom by one quarterwavelength. Both the rod and the strip S3 lie in the plane of thedrawing. The part of the wave guide 2 behind the rod 10 now `forms anininite impedance for electromagnetic waves having a direction ofpolarisation lying in the plane of the drawing. Waves having thisdirection of polarisation are withdrawn substantially entirely from thewave guide Z by the coupling member 9 and are passed to the wave guide12 through the rod 1t).

Transverse slits are provided both in the strip S1 and in the `strip S3.These strips prevent the occurrence of waves of other types. Inparticular no wave types can occur which are produced by longitudinalcurrents in the strips.

The wave guide 2 is coupled at its right-hand end through a matchedtransition piece 13 to a wave guide 14 of rectangular cross-section. Thedirection of polarisation of the electromagnetic waves in the wave guide14 is at right angles to the plane of the drawing.

When the cylinder C is in the position shown, that is to say in theposition in which both the strip S1 and the strip S2 lie in `the planeof the drawing, an electromagnetic wave entering the wave guide 2 fromthe :wave guide 1 will pass unimpeded lfrom the right-hand end of thewave guide 2 to thewave guide 14. Thus, in the wave guide 12 noelectromagnetic wave is produced.

The operation of the power distributor will now be explained withreference to FIG. 2 for the case in ywhich the cylinder C is rotatedfrom the position shown through a certain angle, t'or example an angleot a degrees, an electromagnetic wave being supplied from the wave guide1 tothe wave guide 2.

"FIG, 2 shows co-ordinate axes. The y-axis corresponds to the directionat right angles to the plane of the drawing of FIG. 1, the x-axiscorresponds with a direction in the plane of the drawing of FIG. 1 atright angles to the aixs ofthe wave guide 2.

The vectors -A1-Ay show diagrammatically the electric field strength ofthe electromagnetic waves propagating in the power distributor of FIG. lin the directions of arr-ows P1-Py. The vector A1 represents theelectromagnetic wave supplied from the wave guide 1 to the wave guide 2.The direction of the vector A1 corresponds with the direction ofpolarisation of this wave 4and the length of the vector A1 isproportional to the amplitude of this wave.

FIG. 2 shows the Vector A2 rota-ted relatively to the y-axis through anangle a. This means that the electromagnetic wave in the direction ofthe arrow P2 in FIG. 1 is polarised in a direction rotated through thesame angle a relatively to the direction at right angles to the plane ofthe drawing.

The vector A2 has a component AX in the direction of the x-axis. Thevector Ay represents the wave propagating from the wave guide 2 to thewave guide x14 and the vector AX represents the wave supplied by thecoupling member 9 from the wave guide 2 to the wave guide 12. The ratiobetween the lengths of the vectors Ay and Ax can be simply varied byincreasing or reducing the angle a. Thus, by Varying the position of thecylinder C the raio between the amplitudes of the waves in thewave-guides 12 and 14 and hence the power supplied to either wave guideis varied.

The wave guide 14 of FIG. 1 generally is not terminated withoutreflection. Hence, in the wave guide 14 waves will also propagate in Iadirection opposite to the direction of the arrow Py, as shown by arrowRy.

Similarly to FIG. 2, in FIG. 3 the vectors By-B1 diagrammaticallyrepresent the electric eld strength of the electromagnetic wavespropagating in the direction of the arrows Ry-R1 in FIG. l.

FIG. 3 shows that the vector By has a component By1 3 at right angles tothe strip S2 shown in cross-section and a component Byz tangential tothe strip S2.

The electromagnetic wave represented by the vector Byl propagates alongthe strip S1. Thus, the direction of polarisation yof this wave rotatesthrough an angle a. In the figure this wave is now represented by aVector B1 rotated through an angle a relatively to the vector Byl.

The electromagnetic wave represen-ted by the vector Byz is completelyabsorbed by the strip S2, However, if the 4strip S2 is not present, thiswave reects at the end of the strip S1 and the component of the reectedwave having a direction of polarisation according to the x-axis isguided by the coupling member 9 to the wave guide 12. In this event, thewave in the direction of an arrow PX depends not only upon the wave inthe direction of the arrow P1 Ibut also upon the wave in the directionof the yarrow Ry. The provision of the strip S2 in the manner shownprevents the latter wave from producing an electromagnetic wave in thewave guide 12.

The advantage of the power distributor described consists in that onlythe electromagnetic wave propagating in FIG. 1 from the left to theright supplies power to the wave guide 12. Thus, the power dividerdescribed actually is a directional coupler.

What is claimed is:

1. A microwave power dividing circuit comprising a :source ofelectromagnetic waves of predetermined polarization, rst and secondmicrowave transmission path means for waves of mutually perpendicularpolarization, and polarization rotating coupling means connected tcouple waves from said source to said first and second transmission pathmeans, said coupling means comprising a twistable strip of conductivematerial extending axially of said coupling means between said sourceand said rst and Second transmission means, means -for twisting saidstrip for rotating the polarization of said waves, and `a rotatableabsorbing strip of material for absorbing electromagnetic energy, saidabsorbing strip being positioned between said twistable strip and saidrst and second transmission path means in a longitudinal plane withrespect to said coupling means, said absorbing strip being in the Sameplane as the end of said twistable strip toward said rst and secondtransmission .path means.

2. A microwave power dividing circuit comprising a source ofelectromagnetic waves of predetermined polarization, first and secondrectangular waveguide means having mutually perpendicular polarizations,and polarization rotating coupling means for coupling said waves to saidiirst and second waveguide means, said coupling means comprisingcircular waveguide means, means applying said waves to one end of saidcircular waveguidt-l means, means for coupling said first and secondrectangular waveguide means to the other end of said circular waveguidemeans, a twistable 4strip `of `conductive material posi- `tioned withinsaid circular waveguide means and extending axially therewith, means`for twisting Said twistable strip, and a rotatable strip ofelectromagnetic energy absorbing material within said circular waveguidemeans between `said twistable strip and said other end, said energyabsorbing `strip ybeing positioned in a plane extending through the axis`of said circular waveguide means, said adjustable strip being in thesame plane as the adjacent end of said twistable Strip.

3. A microwave power dividing circuit comprising a source ofelectromagnetic Waves of predetermined polarization, -rst and secondrectangular waveguide means having mutually perpendicular polarizations,land polarization rotating coupling means for coupling said waves tosaid first and second waveguide means, Said coupling means comprisingcircular waveguide means, means applying Said waves to one end of saidcircular waveguide means, means `for coupling said tirst and secondrectangular waveguide means to the other end of said circular waveguidemeans, a twistable strip of conductive material positioned within saidcircular waveguide means and extending axially therewith, means forholding the end of said twistable strip toward said one end of sa-idcircular waveguide means, means for rotating the other end of saidtwistable strip for twisting said strip, `a strip of electromagneticenergy absorbing material mounted on said other end of said twistablestrip, said energy absorbing strip lbeing positioned in a planeextending through the axis of said circular waveguide means and being inthe same plane as said `other end of said twistable strip.

References Cited in the tile of this patent UNITED STATES PATENTS2,628,278 Zaleski Feb. 10, 1953 2,748,352 Miller May 29, 1956 2,769,145Zaleski et al. Oct. 30, 1956 2,942,266 Mattingly June 2l, 1960 2,985,850Crawford et al May 23, 1961

1. A MICROWAVE POWER DIVIDING CIRCUIT COMPRISING A SOURCE OFELECTROMAGNETIC WAVES OF PREDETERMINED POLARIZATION, FIRST AND SECONDMICROWAVE TRANSMISSION PATH MEANS FOR WAVES OF MUTUALLY PERPENDICULARPOLARIZATION, AND POLARIZATION ROTATING COUPLING MEANS CONNECTED TOCOUPLE WAVES FROM SAID SOURCE TO SAID FIRST AND SECOND TRANSMISSION PATHMEANS, SAID COUPLING MEANS COMPRISING A TWISTABLE STRIP OF CONDUCTIVEMATERIAL EXTENDING AXIALLY OF SAID COUPLING MEANS BETWEEN SAID SOURCEAND SAID FIRST AND SECOND TRANSMISSION MEANS, MEANS FOR TWISTING SAIDSTRIP FOR ROTATING THE POLARIZATION OF SAID WAVES, AND A ROTATABLEABSORBING STRIP OF MATERIAL FOR ABSORBING ELECTROMAGNETIC ENERGY, SAIDABSORBING STRIP BEING POSITIONED BETWEEN SAID TWISTABLE STRIP AND SAIDFIRST AND SECOND TRANSMISSION PATH MEANS IN A LONGITUDINAL PLANE WITHRESPECT TO SAID COUPLING MEANS, SAID ABSORBING STRIP BEING IN THE SAMEPLANE AS THE END OF SAID TWISTABLE STRIP TOWARD SAID FIRST AND SECONDTRANSMISSION PATH MEANS.